Upper plane and lower plane of a substrate are parallel in conventional technology. Active layer formed on the upper plane is conventionally parallel to the upper plane and lower plane of a substrate. In addition, the ordinary outer plane of a chip with hexahedron shape is a rectangular cutting section. The shape of each layer revealed on the cross sections facing outside is straight lines, which is equivalent to a case of an artificial cross section imaginably formed perpendicular to the outer plane inside the chip.
(Non-patent reference 1) “Nitride-Based LEDs with Textured Side Walls”
(Non-patent reference 2) IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 16, NO. 3, pp 750-751 MARCH 2004
(Non-patent reference 3) “Nitride-Based LEDs with Phosphoric Acid Etched Undercut Side Walls”
(Non-patent reference 4) IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 21, NO. 8, pp 510-512 Apr. 15, 2009.